The subject invention relates to determining the position of a rotor in a machine such as a motor or a generator. More particularly, the subject invention relates to determining the position of a rotor by identifying an axis of magnetization.
Identifying the axis of magnetization of a machine allows the control of a power flow in the machine. Machines that use rotors with permanent magnets often use sensors to identify the axis of magnetization. Sensors increase the complexity of a system, and may be undesirable. Combining Terminal voltage and line current into an estimation of machine EFLUX allows for the identification of the axis of magnetization. The determination of machine EFLUX to identify the axis of magnetization is effective while the machine is operating at high speeds because the machine has a readily measurable EFLUX, however as the Machine terminal voltage decreases with the decrease in speed of the machine, the effectiveness of the determination is reduced. When the machine is stationary, and there is no machine terminal voltage related to related to the speed, and a determination of rotor position using terminal voltage to indirectly measure EFLUX is ineffective.
U.S. Pat. No. 6,401,875 teaches method to used such described change in inductance to identify axis of magnetization, the method does not teach mean to detect other than zero speed and restricts stimulas to apriory shape and is not readily extensible to less predefined waveshape as would be anticipated in zero current regulation for instance.
Therefore, a system and method that allows the identification of the axis of magnetization of a stationary high as well as low speed machine is desired.